Many industrial products when wet or when subjected to treatment in water are normally susceptible to bacterial and/or fungal degradation or deterioration if means are not taken to inhibit such degradation or deterioration. Wood pulp, wood chips, starch and proteinaceous substances, animal hides, vegetable tanning liquors, and leather are all damaged or degraded by growth of bacteria and other microorganisms or by enzymes produced by such growth. Wet pulp containing about 25 percent moisture content is subject to attack by stain, mold, and decay fungi. If not controlled, the result is a loss of useful fiber in badly decayed pulp, difficulty in dispersing partially decayed pulp, a darkening in color, and the development of undesirable odors caused by the growth of the microorganisms. Different species of molds are encountered at various stages in the manufacture of leather. As an example, soaking provides an environment highly conductive to the growth of microorganisms, and even strong pickle solutions are subject to attack by some microorganisms. Molds in particular may be troublesome and cause discoloration of the pickled stock, especially if it is held for a period of time. During the chrome tanning process, the chrome tanned stock held "in the blue" readily molds and is discolored. Mold growth may develop on heavy vegetable tanned leather during the drying period and produce spots and stains on either the flesh or grain sides.
Another objectionable phenomenon occurring in industrial process systems involving water is slime formation. Slime consists of matted deposits of microorganisms, fibers, and debris, and it may be stringy, pasty, rubbery, tapioca-like, hard, or horny, and it may have a characteristic odor that is different from that of the liquid suspensions in which it is formed. The microorganisms involved in its formation are primarily different species of spore-forming and nonspore-forming bacteria, particularly capsulated forms of bacteria which secrete gelatinous substances that envelop or encase the cells. Slime microorganisms also include filamentous bacteria, filamentous fungi of the mold type, yeasts, and yeast-like organisms.
Besides being objectionable from the standpoint of general cleanliness and sanitation in breweries, wineries, dairies, paper mills, and other industrial plants or establishments, slime may interfere and produce plugging of screens in pulp and paper systems, thus reducing their efficiency. When large amounts of slime become incorporated in the paper sheet, its strength is reduced, and it may consequently break and require rethreading of the machine. In the paper itself, slime may be responsible for unsightly spots, holes, and odors and may produce general discoloration throughout the sheet.
Sulfate-reducing bacteria are generally present in waters used for the secondary recovery of petroleum. The presence of these bacteria is objectionable if not controlled. For example, these organisms are able to reduce sulfates present in the injection water to sulfides which in turn react with soluble iron salts to form insoluble iron sulfide. As a result, matted deposits are produced consisting of sulfides, occluded oil, plus any other solids that may be present. This is undesirable because water containing such deposits when injected into subterranean formations causes the plugging thereof. Furthermore, sulfate-reducing bacteria cause corrosion of metal by accelerating galvanic action. Microbiological corrosion is well recognized and is a major economic problem in the petroleum industry.
It is, therefore, a principal object of the present invention to provide a synergistic composition for the control of microorganisms that are responsible for the formation of slime in aqueous systems.
It is another object of this invention to provide an improved process for controlling slime-forming microorganisms in aqueous systems such as pulp and paper mill systems, cooling water systems, and secondary recovery petroleum operations.
These and other objects and advantages of the novel compositions and processes of this invention will become apparent as the description proceeds.
To the accomplishment of the foregoing and related ends, this invention then comprises the features hereinafter fully described and particularly pointed out in the claims, the following description setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the various ways in which the principles of the invention may be employed.
In brief, the foregoing objects and advantages are obtained by utilizing compositions comprising synergistic mixtures of 2-(thiocyanomethylthio)benzothiazole and 2,2-dibromo-3-nitrilopropionamide.
The compositions of this invention are utilized for controlling the growth and reproduction of slime-forming microorganisms by adding the compositions to cooling water systems, pulp and paper mill systems, pools, ponds, lagoons, lakes, etc., in an amount sufficient to control the slime-forming microorganisms which are present in the system which is treated.
The organic microbicides comprising the compositions of this invention are commercially available compounds or easily synthesized from commercially available raw materials. The preparation of 2-(thiocyanomethylthio)benzothizaole is described in U.S. Pat. No. 3,520,976. The 2,2-dibromo-3-nitrilopropionamide is a commercially available microbicide manufactured by the Dow Chemical Company of Midland, Michigan.
The ratios of the 2-(thiocyanomethylthio)benzothiazole to 2,2-dibromo-3-nitrilopropionamide in the compositions of this invention are adjusted to provide a synergistic behavior to the composition. These synergistic weight ratios range from about 90:10 parts of 2-(thiocyanomethylthio)benzothiazole to 10:90 parts of 2,2-dibromo-3-nitrilopropionamide. When the microbicides are present in these ratios, the resulting composition possesses a higher degree of effectiveness against microorganisms than the individual microbicides comprising the mixture.
As to the amount of the compositions to be added to the various systems, suitable and preferred quantities vary according to the specific system in which the compositions are used. When added to aqueous systems to control slime-forming microorganisms, the suitable and preferred quantities vary from 0.01 to 5000 parts and 0.1 to 1000 parts, respectively, per million parts of water present in the system. It will be understood, of course, that larger quantities of the compositions may be used with no detrimental effect, but such larger quantities increase the cost of treatment with limited material benefit.
In order to disclose the nature of the invention still more clearly, the following illustrative examples will be given. It is understood, however, that the invention is not to be limited to the specific conditions or details set forth in these examples, except insofar as such limitations are specified in the appended claims.